Sectioned 25 Pdr fuse.
   (Ver 1)


WARNING: This fuse came from a known supply of parts and did not contain explosive. It was sectioned by someone who knows what he is doing.
Any work on explosive devices should only be undertaken by a qualified armourer, as unlike this fuse, which came from a scrap source years ago, most that are found dumped still have the explosive in place (which is why they were dumped) and are highly dangerous and should be left where they are and the authorities notified so they can be rendered safe. Fuses that were primed were sealed with a substance that appears to be "Stag Brand" pipe thread sealant. The workmanship and quality of the paste is such that the explosive can be still dry and dangerous (more so the older it is) regardless of how corroded, how deep in water or how long it has been there or what is claimed by anyone.

There appears to be 2 versions of this model of fuse, lets call them type 1 and type 2:
TYPE 1 - the one you see here, has a windshield made of alloy and the fuse itself is made from bronze.
TYPE 2 - where the bottom most insert - the magazine labelled (I) - was made of alloy.
From enough fuses to fill a 44 gallon drum came 3 of type 1 and the rest were type 2.



Download the big pics by clicking on the small pics...


What it all does:

A) Is the initial safety, this rod shaped piece of brass is set back by the force of the round being pushed forward when the gun is fired.

B) Another safety, cannot move unless (A) has been set back, providing this criteria has been met, (B) is forced outwards by the spin imparted by the rifling of the gun.

C) Is the last safety, it is also a rotation activated safety, this is a shutter type safety and it moves (to the left rear in this cut away) in its slot and is held there against a spring by the continued spin of the round. The spring is located directly behind it and is not visible in this picture. Should the round not be spinning, it will return to its resting position as shown here. Drilled from the bottom upwards is a small hole in the shutter. This hole does break through the top of the shutter, thus a thin remnant of brass remains. This hole is not in alignment with magazine (H) unless the shutter is held against its spring by rotation of the round.

D) Only when all the above criteria are met is the round ready to explode on impact. This is initiated by the firing pin carrier moving forward against its spring and ramming the firing pin into the primer (E).

E) Is detonated and the fire front moves down the channel in the side of the carrier (F).

F) This channel takes the fire from the front of the fuse and directs it to the first magazine (G).

G) Is then detonated and a new fire created, which expands into chamber (H).

H) Is dependant on shutter (C) being held by the spin of the round so that the blanked off hole in the shutter is in alignment with (H).

I) Is the magazine. Providing that shutter (C) is held in the armed position with the blanked hole in alignment with chamber (H) the flame front can burst through the thin blank at the bottom of the hole in the shutter and detonate the magazine. This in turn detonates the shell.

J) Is a combination of streamlining for ballistic purposes and a standoff to give a slight delay. Essentially the small amount of time it takes for the alloy nose cavity to crush down to the bronze metal is a time delay for ground penetration.

K) Had me puzzled, it turns out this is removal of material to balance the fuse.

If anyone can supply a decode for the numbers stamped into 25 Pdr fuses, particularly Australian ones it would be most appreciated. Even just the factory identifiers for ANY munitions factory would be a help.
This fuse has the following stamped into it "KBY 6 42 315", presumably this is a June 1942 production. But as to what the "KBY" and "315" mean is a mystery.
Australian ammunition was made in some pretty unlikely places and it would be a real break through to learn the codes for the factories. Probably the most unlikely location of all was the small gold mining town of Kalgoolie. There was a large stock of unfilled 40mm Bofors projectiles at a scrap yard in Wodonga, Victoria for years until it was cleared and these turn up all the time in Australia. Quite conveniently they were still boxed and the boxes were clearly marked. Thus the codes are known for Kalgoolie.
But the produce of such places as my home town of Broken Hill where 25 Pdr fuses were made in a purpose built factory which is now the TAFE college, cannot be identified. The one and only fuse I have been able to track down which is definetly a Broken Hill product is a sectioned example like the one above and was presented to a female worker at the end of the war, she is still alive at the time of writing this article and I have verified the facts with her - it is a type 1 fuse. It was not stamped at all, so is of no help.


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